Rising temperature slows global major food production

The world’s rising temperature is slowing production of major food crops, and as global warming continues, the trend will significantly disrupt the economies of many countries and impair the health of their people, Stanford researchers say.

A single degree increase in global temperature can result in a 5 percent drop in the world's production of corn

If the impact is to be averted, farmers in many parts of the world will have to change the types of crops they grow, and the planting of many crops – particularly corn and wheat – will have to be shifted to regions where they are not now grown.

The findings are the result of a detailed global study of climate change and its links to food production by the Stanford group, together with a Columbia University economist, who looked closely at the past 30 years of production for four of the world’s major food crops – corn, wheat, rice and soybeans.

Rice, soybeans stable

They found that only rice and soybean crops have remained relatively unaffected by climate change. But global corn production was nearly 4 percent lower than it might have been if that warming trend hadn’t existed, and the world’s wheat crop was 5.5 percent lower than normal. The decreased output may well be responsible for a 6 percent rise in global prices for those two food crops over the three decades, they found.

The exceptions were the United States, Canada and northern Mexico, where temperatures overall haven’t risen in the past 30 years, nor has production of the crops decreased. The economists say they couldn’t explain it.

“It appears as if farmers in North America got a pass on the first round of global warming,” said team leader David B. Lobell, an assistant professor of environmental Earth system science at Stanford University, in a statement. “That was surprising, given how fast we see weather has been changing in agricultural areas around the world.”

In the online journal Science Express published Thursday, the researchers said they examined corn, wheat, rice and soybeans because they are a key signal for all the varied foods consumed by people around the world. They used computer modeling from widely available crop and climate data, and the report is complex and statistical, but its implications are clear: The warmer the world gets, the more threatened much of the food supply becomes.

Effects on health

Computer modeling shows that every increase of a single degree in global temperatures can result in a 5 percent drop in the world’s production of those crops, Lobell’s group reported.

In an e-mail interview, Lobell said there is no question that global warming is curbing crop production, which, in turn, is resulting in higher food prices. And that, he said, can have direct consequences to health.

The four crops he and his colleagues studied are humans’ most important sources of calories. “There are millions who spend a large part of their income on food, and a price increase would cause them to reduce food consumption,” he said.

Fewer calories could lead to more malnutrition and illness for those least able to pay for the food.

Worldwide temperatures have risen by less than a degree in the past 30 years, and as climate change continues, farmers will need to adapt by planting new crop varieties resistant to higher temperatures, and some crops will move to farmlands farther north, where temperatures are lower, the analysts say.

Working with Lobell on the analysis were Justin Costa-Roberts, a Stanford computer science graduate student, and Wolfram Schlenker, a Columbia agricultural economist.